The present invention is related to a method and a device for manufacturing string core-free invisible zipper. By means of the method and the device, the zipper racks can be totally independently and naturally loosely fed into the needle seat and sewn on the fabric belts. It is not necessary to first forcedly stretch open the two racks prior to feeding the racks into the needle seat. Accordingly, the zipper racks are prevented from being tensioned and deformed or curled and the pitch will be unified and the racks can be precisely sewn on the fabric belts.
A zipper is applied to a clothes or a purse for quickly putting on or taking off the clothes. A conventional zipper includes a pair of fabric belts and zipper racks sewn on opposite lengthwise edges of the fabric belts and a slider slidable along the edges for zipping on/off the zipper. The zipper teeth of a traditional zipper are exposed between the two fabric belts so that the appearance is poor. An invisible zipper has been developed. The connecting sections of the zipper teeth are hidden in the reversely folded edges of the fabric belts so as to achieve better appearance.
In the conventional invisible zipper, the zipper rack is made in such a manner that a zipper wire material is spiraled or wound and drawn on a thread rod. During drawing, the wire is heated and molded. After molded, the zipper rack needs to overcome the twisting and deformation after cooled. Therefore, after molded, the slider is used to force the two independent zipper racks to mesh with each other and then curl and collect. Due to the drawing, even though the zipper racks are engaged with each other, the pitch will be still ununified and the zipper rack will bend and tangle. Therefore, a reinforcing string core is passed through the loops of the zipper for pulling and retaining the zipper rack so as to avoid twisting and deformation thereof. However, when feeding the zipper rack and fabric belt into the needle disc of the machine for sewing, the two lateral racks must be separately reversely fed in and sewn on the fabric belts. After sewn, the slider is used to zipper on the racks. Therefore, prior to feeding into the needle disc, in a conventional zipper making machine, a zipper rack separating bar 7 is disposed in front of the entrance of the needle disc for forcedly separating the zipper racks. Then, the racks 6 are intersectionally reversely fed into the needle seat 5 of the machine (referring to FIG. 7). In addition, in order to overcome the curling of the racks 6 which cannot be placed straight into the needle seat 5 for sewing, inward flanges 511 are disposed at top end of the guiding channel 51 of the needle seat 5, whereby when guiding in the racks 6, the flanges press and hold the racks 6 and prevent the racks 6 from bending up and separating from the channel 51 to interrupt the operation. The guiding gap 51A of the needle seat 5 at the sewing board 52 is smaller than the gap of the front section of the guiding channel 51. Accordingly, when feeding in the racks, the racks will be deflected and damped. This makes it difficult to sew and locate the racks. Moreover, prior to feeding the racks into the needle seat 5, the separating bar 7 will separate the engaged racks 6. Accordingly, the racks 6 will suffer an undesired pulling force prior to sewing operation. Under the double additional pulling force, the pitch of the racks 6 will be changed and ununified. After sewn, the racks on two sides can hardly precisely mesh with each other. Therefore, the zipper tends to unlatch or it will be hard to slide the slider.
It is therefore a primary object of the present invention to provide a method and a device for manufacturing string core-free invisible zipper. Without string core, the molded zipper racks are separately and directly loosely reversely fed into the needle seat of the machine. The fabric belts are at the same time fed into the needle seat for sewing the zipper racks thereon. Prior to feeding the racks into the needle seat, it is not necessary to use a rack separating bar to forcedly stretch open the two racks. Accordingly, the zipper racks are prevented from being tensioned and deformed or curled and the pitch will be unified. The slider can more smoothly slide without being obstructed. The teeth of the racks can more firmly mesh with each other.
It is a further object of the present invention to provide the above method and device in which the guiding channels of the needle seat pass through the entire needle seat and have unified width so that the racks can be fed in without being obstructed and unevenly tensioned. Therefore, the zipper racks are prevented from being tensioned and deformed and the pitch will not be deflected and can be precisely sewn on the fabric belts.
It is still a further object of the present invention to provide the above method and device in which the zipper rack itself is straight without twisting so that it is unnecessary to additionally pass a reinforcing string core through the zipper rack. Therefore, the processing procedure can be omitted and the cost for the zipper rack is reduced.
The present invention can be best understood through the following description and accompanying drawings wherein: